U.S. Pat. No. 3,299,812 relates to ammunition for stud drivers, rifles and the like, which includes an electric ignition cartridge comprising a pellet of a deflagrating explosive, e.g. a double based smokeless powder grain, containing nitrocellulose and nitroglycerin, plated with a thin metal coating, which is heated by the passage of an electric current to a temperature sufficient to ignite the adjacent surface portion of the explosive.
A principal problem in the production of a resistance electrical ignition system (REIS) of the aforesaid type utilizing a metal plated film or grain of a nitrocellulose base deflagrating explosive, hereinafter referred to as propellant, is that the nitrocellulose because of its smooth surface does not plate well with conventional commercial electroless plating reagents. For this reason, it is difficult to obtain a metal coating, which possesses good adhesion to the nitrocellulose substrate and resistance to electrical breakdown, a common troublesome factor in attempts to ignite the nitrocellulose propellant by means of an electrical current. This tendency to electrical breakdown is a major obstacle in developing REIS igniters, which ignite with sufficient speed by application of an electric current so as to be suitable for use in fast acting propellant devices, such as cannon, rockets, pyrotechnic devices, etc. Speed of ignition is related among other things to voltage of the DC power supply used to ignite the REIS device. However, as the DC voltage is increased to reduce the ignition delay with electrolessly deposited copper or other metal films on nitrocellulose substrates, there is a tendency for the metal film to rupture, which results in loss of its ability to further carry any current.
One method for providing a fairly satisfactory surface for electroless plating of metals is to roughen the nitrocellulose propellant substrate mechanically with fine emery cloth, ground glass, grinding powder, etc. It is thought that the roughened surface enables the palladium or other catalyst conventionally employed to be deposited more effectively, thereby promoting adherence of the electrolessly plated metal coating. However, from the standpoint of mass production of such metal plated nitrocellulose base REIS igniters, surface conditioning by mechanical pretreatment is objectionable, since it requires special equipment, extended process time or at least considerable hand labor and hence involves expensive operations.